Accelerated secondary display system

ABSTRACT

An accelerated secondary display system comprising a display adapter with a display simulator, a host computer with host software, a client device with a screen and client software. The display simulator is configured to send display characteristics to the host computer. The host computer is configured to receive the display characteristics and render an image with hardware acceleration into a frame buffer. The host software is configured to cause the host computer to stream image data over a communication channel, the image data based on the image in the frame buffer. The client software is configured to receive the image data over the communication channel and present a copy of the image on the screen based on the image data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/461,990, filed 22 Feb. 2017, incorporated herein by reference.

TECHNICAL FIELD

This specification relates to computer hardware and software. Moreparticularly, the present specification relates to video displays andmobile devices.

BACKGROUND

Many computer users work on the go, and are frustrated by the smallscreen of a laptop computer. Many of these users also carry with them amobile device, in addition to a laptop computer. There is a need for asolution that allows computer users to use a device with a screen, suchas a tablet, mobile phone, or another computer, as a monitor for acomputer.

Numerous solutions are commercially available today that allow a clientdevice with a screen to be used as a display for a host computer. Withone exception, these systems convince the host computer that a physicaldisplay is connected by implementing a virtual video driver. The oneexception is Air Squirrels' clever Reflector software, which implementsa receiver for Apple's AirPlay protocol. But Reflector, which uses ahacked copy of Apple's private key, is a fragile solution that cannot besold in Apple's ecosystem, can be broken by a change in Apple's AirPlayimplementation at any time, and because it uses a pirated private key,is ethically questionable.

The other solutions all employ virtual video drivers. These virtualvideo drivers are full software drivers that convince the host computerthat a physical display is connected. The host computer then renders thecontents of that display into a frame buffer in memory. In turn, hostsoftware repeatedly streams the contents of that frame buffer to someexternal device. This is a suboptimal solution for several reasons.

In general, virtual video drivers are not associated with any physicalgraphic-acceleration hardware. Consequently, they are subject to severeperformance and compatibility limitations, because most modernperformance-dependent software is optimized to perform graphicsoperations with a graphics accelerator. In the absence of hardwaregraphics acceleration, many apps fail to render some user interfaceelements, render incorrectly, or crash completely. And virtual videodrivers are fragile on macOS because Apple has not made its video driverprotocols public and changes those protocols frequently.

One commercially available virtual video driver solution supportshardware graphics acceleration. That one, Avatron's Air Display Host forWindows (U.S. Pat. No. 9,058,759 B2), is fragile and very complicated,because it attempts to implement the entire application-level renderingstack. Furthermore, because Microsoft routinely adds features andcomplexity to its graphic acceleration driver specification, thathardware-accelerated Air Display Host needs to be updated frequently tostay compatible with Windows—and that approach only works on Windows.

At the same time, modern computer operating systems, such as macOS andWindows, do allow hardware graphics acceleration for monitors that areconnected to their video output ports, such as HDMI (High-DefinitionMultimedia Interface), VGA (Video Graphics Array), Mini DisplayPort, andMini DVI (Digital Visual Interface). Displays connected to these portsare driven by the computer's own video drivers, which in modern personalcomputers do feature graphics acceleration hardware. These operatingsystems do not, however, allow such automatic graphic acceleration fordisplays connected via Wi-Fi (Wireless Fidelity), USB (Universal SerialBus), or custom cables. So, displays plugged into the standard videoports are fast and compatible, while those that are connected via othermethods are not.

There is a recent development called a display simulator. Sometimes itis called by the misnomer “headless accelerator,” but it is not anaccelerator. It is a dongle, i.e., a small device that plugs into avideo port (such as HDMI, DisplayPort, or VGA) and convinces thecomputer that it is a real display. In its simplest form, it is just aresistor plugged into two pins of a VGA port, but it can also be a smallboard with memory and controller chips, reporting display descriptorsvia DisplayID or EDID blocks. The display simulator does not displayanything on a monitor, but it does convince a computer that something isplugged into a video port. In response, the computer dutifully uses itsgraphics accelerator to render into the frame buffer that it hasassociated with the phantom display. Display simulators are designed for“headless” servers, which have no physical display. They convince aserver computer that a monitor is connected so that the server can useits GPU for accelerated rendering. But it doesn't provide a secondarymonitor.

SUMMARY

Described herein is a system that includes a display simulator, therebyenabling a host computer to employ its own hardware graphicsaccelerator(s) for a secondary monitor on a separate computing clientdevice while software running on the host computer communicates, via adata port or Wi-Fi, with software running on the client device. Thisallows fast performance and good compatibility, without requiring afragile virtual video driver, to use the secondary device's screen as asecondary monitor for the host computer.

The system connects a display simulator into a host computer's standardvideo port, thereby getting the host computer to use its own videodriver to render a changing image with hardware acceleration into aframe buffer in memory, while streaming that frame buffer's contents toan external device. One embodiment of this system comprises hostsoftware running on a host computer, client software running on asecondary client device, and a hardware adapter that includes a displaysimulator. In this embodiment, the host software on the host computersends the contents of the frame buffer over a communication channel,such as USB, Wi-Fi, or Ethernet, to the client software on the clientdevice, which in turn displays the screen contents on the clientdevice's display.

Because this system does not require a virtual video driver, it is morerobust than prior art, as it needs to conform only to well-documentedpublicly available hardware protocols. It is faster than a software-onlyvirtual video display, because it derives the benefit of the hostcomputer's hardware-accelerated video driver. It is more compatible withother software on the host computer that behaves best when anaccelerated video driver is available. It is easier to maintain becauseit does not have the complexity of a virtual video driver.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more embodiments of theinventive subject matter and, together with the detailed description,serve to explain the principles and implementations thereof. Likereference numbers and characters are used to designate identical,corresponding, or similar components in different figures. The figuresassociated with this disclosure typically are not drawn with dimensionalaccuracy to scale, i.e., such drawings have been drafted with a focus onclarity of viewing and understanding rather than dimensional accuracy.

FIG. 1 is a view of a first embodiment of an accelerated secondarydisplay system.

FIG. 2 is a view of a second embodiment of an accelerated secondarydisplay system.

FIG. 3 is a view of a third embodiment of an accelerated secondarydisplay system.

DETAILED DESCRIPTION

In describing the one or more representative embodiments of theinventive subject matter, use of directional terms such as “upper,”“lower,” “above,” “below”, “in front of” “behind,” etc., unlessotherwise stated, are intended to describe the positions and/ororientations of various components relative to one another as shown inthe various Figures and are not intended to impose limitations on anyposition and/or orientation of any component relative to any referencepoint external to the Figures.

In the interest of clarity, not all of the routine features ofrepresentative embodiments of the inventive subject matter describedherein are shown and described. It will, of course, be appreciated thatin the development of any such actual implementation, numerousimplementation-specific decisions must be made in order to achievespecific goals, such as compliance with application and business-relatedconstraints, and that these specific goals will vary from oneimplementation to another and from one developer to another. Thoseskilled in the art will recognize that numerous modifications andchanges may be made to the representative embodiment(s) withoutdeparting from the scope of the claims. It will, of course, beunderstood that modifications of the representative embodiments will beapparent to those skilled in the art, some being apparent only afterstudy, others being matters of routine mechanical, chemical andelectronic design. No single feature, function or property of therepresentative embodiments is essential. In addition to the embodimentsdescribed, other embodiments of the inventive subject matter arepossible, their specific designs depending upon the particularapplication. Any embodiment described as “comprising” includes the caseof “consisting only of.” The scope of the inventive subject mattershould not be limited by the particular embodiments herein described butshould be defined only by the appended claims and equivalents thereof.

Common Features of the Embodiments

FIGS. 1, 2, and 3 show first, second, and third embodiments ofaccelerated secondary display systems (100, 200, 300). The basiccomponents of an accelerated secondary display system are a displayadapter (102, 202, 302) with a display simulator (122, 222, 322), hostsoftware (124, 224, 324), and client software (126, 226, 326). The hostsoftware (124, 224, 324) is configured to be loaded into and executed bya host computer (106, 206, 306). The client software (126, 226, 326) isconfigured to be loaded into and executed by a client device (118, 218,318). The various embodiments incorporate different auxiliary componentsto enable communication between the host software (124, 224, 324) andclient software (126, 226, 326), or to connect the display simulator(122, 222, 322) to the host computer (106, 206, 306).

The display simulator (122, 222, 322) is configured to connect to thehost computer (106, 206, 306). It might be plugged directly into a videoport (e.g. 238, 338), hard-wired to an internal hub (e.g. 108) in theadapter (e.g. 102), or connected via some other mechanism. Once thedisplay simulator (122, 222, 322) is connected, it reports displaycharacteristics to the host computer (106, 206, 306) via a standardprotocol, such as DisplayID or EDID (Extended Display IdentificationData), supported by the host computer (106, 206, 306). These protocolsspecify display capabilities and characteristics of a generic clientdevice. Then the host software (e.g. 124, 224, 324) can override thosegeneric capabilities and characteristics, if necessary, to correctlyreflect the capabilities and characteristics of the actual connectedclient device (118, 218, 318). The capabilities and characteristics, asdefined by the DisplayID and EDID protocols, include one or more suchdescriptors as manufacturer ID, date of manufacture, product code, colorspace, and supported resolutions and timings.

When connected to the display simulator (122, 222, 322), the hostcomputer (106, 206, 306) uses its own display hardware adapter anddriver(s) to instantiate a frame buffer in memory. The host computer(106, 206, 306) renders an image with hardware acceleration into theframe buffer. The image typically changes over time. The frame buffermaintains pixels of the image to be presented on a screen. But since thedisplay simulator (122, 222, 322) is not a real display, no pixels areactually visible unless the host software (124, 224, 324) running on thehost computer (106, 206, 306) streams image data based on the contentsof the frame buffer to some other device with a screen, such as theclient device (118, 218, 318).

The host software (124, 224, 324), running on the host computer (106,206, 306), streams image data based on the frame buffer's pixels over acommunication channel, such as Wi-Fi, USB, Bluetooth, or Ethernet, tothe client software (126, 226, 326), which is running on a client device(118, 218, 318). In some embodiments, the host software (124, 224, 324)does this simply by repeatedly copying the entire frame buffer andsending copies of the raw pixel data as image data to the clientsoftware. In other embodiments, the host software (124, 224, 324) ismore efficient, conserving bandwidth and/or processor power, and/or toyield a better frame rate. In some embodiments, the host software (124,224, 324) subscribes to notifications from the host operating systemthat notify of changed regions in the frame buffer. The host software(124, 224, 324) only sends as image data copies of those pixels thathave actually changed, when they have changed. In some embodiments, thehost software (124, 224, 324) aggregates overlapping change regions toavoid sending duplicate copies of the same pixels. In some embodiments,the host software (124, 224, 324) employs a compression algorithm suchas JPEG, PNG, MPEG, H.264, or a custom image-compression algorithm, toreduce data size of the image data. In some embodiments, the hostsoftware (124, 224, 324) converts pixels into a more efficient colorspace, such as YUV or 4:2:2 YCbCr, rather than RGB, to speed upcompression. In some embodiments, the host software (124, 224, 324)parallelizes the pixel copying, compression, and sending as image data,both on the CPU and on the GPU. In some embodiments, the host software(124, 224, 324) optimizes parallel processing by dividing the framebuffer's pixels into tiles or bands.

The host software (124, 224, 324) sends the image data to the clientsoftware (126, 226, 326), along with metadata to assist the clientsoftware (126, 226, 326) to display the image data. In some embodiments,the metadata includes a protocol version number, the frame buffer'sresolution, and a specification of a video compression codec used. Theclient software (126, 226, 326) receives the metadata and image datafrom the host software (124, 224, 324), decompresses and/or convertscolor spaces if necessary, and based on the image data, displays copy ofthe image on the screen of the client device (118, 228, 328). The imagedisplayed on the screen of the client device (118, 228, 328) is an exactor near copy of the image comprising the pixels in the frame buffer ofthe host computer (106, 206, 306).

In some embodiments, the client software (126, 226, 326) also streamsdata back to the host software (124, 224, 324). Such data includes oneor more of: The client device's native screen resolution; currentorientation (landscape or portrait); and supported protocol versions.

In some embodiments, the client software (126, 226, 326) senses touchevents on the screen of the client device (118, 218, 318) and streamsdata to describe those events back to the host software (124, 224, 324).The client software (126, 226, 326) may recognize special gestures forspecific mouse actions. Examples may include two-finger tap for asecondary mouse click, or two-finger drag for a scroll-wheel event. Ifthe client device (118, 218, 318) supports pressure sensitivity, theclient software (126, 226, 326) can send pressure data to the hostsoftware (124, 224, 324), which in turn can synthesize pressure eventsto which the host computer (106, 206, 306) will respond as it would to aconnected pressure-sensitive stylus.

The host software (124, 224, 324) may stream audio as well as video. Ifrunning on a client device with a camera, some embodiments of the clientsoftware (126, 226, 326) cause the client device (118, 218, 318) to actas a virtual web camera for the host computer (106, 206, 306). If theclient device has a microphone, some embodiments the client software(126, 226, 326) cause the client device (118, 218, 318) to act as avirtual microphone for the host computer (106, 206, 306). In someembodiments, the client software (126, 226, 326) causes the clientdevice (118, 218, 318) to act as a virtual keyboard, detecting andsending keystrokes for the host software (124, 224, 324).

First Representative Embodiment

As shown in FIG. 1, the first embodiment accelerated secondary displaysystem 100 comprises a first embodiment display adapter 102, firstembodiment host software 124, and first embodiment client software 126.The host software 124 is configured to load into and run on a hostcomputer 106 that has a data port 104 that is USB-C compliant. Theclient software 126 is configured to load into and run on a clientdevice 118 with a client data port 116.

The display adapter 102 has a hub 108 that splits an adapter dataconnection cable 109 into three output ports: a first adapter data port110 that is USB-A compliant, a second adapter data port 114 that isUSB-C compliant, and a video port 120 that is HDMI (High-DefinitionMultimedia Interface) compliant. The hub port is configured to connectto the host data port 104 via a cable. The first adapter data port 110is configured to connect via a cable to the client data port 116 on theclient device 118. The second adapter data port 114 is configured toconnect to an AC power adapter 112. The adapter video port 120 isconnected to a display simulator 122. In the first embodimentaccelerated secondary display system 100, the host software 124communicates with the client software 126 via a communication channelthat is USB-3 compliant. The client data port 116 may be, for example, aLightning port or 30-pin dock connector port on an iOS device or amicroUSB port on an Android device. In some alternative embodiments, thecommunication between the host software 124 and the client software 126is handled by a wireless communication channel, similar to the secondembodiment accelerated secondary display system 200.

The hub 108 inside the display adapter 102 is functionally equivalent toa “USB Type C to HDMI+USB Type A+Type C Power Charging Port Multi HubCombo Adapter,” which is commercially available from many vendors. Sincethe HDMI port is not exposed externally, some components of the hub 108can be eliminated, notably the bridge chip. The power-charging port isnot in all embodiments, because most host computers have a separatepower-charging port.

Second Representative Embodiment

The second embodiment, shown in FIG. 2, is simpler than the firstembodiment and is compatible with a host computer with an HDMI videoport. The second embodiment accelerated secondary display system 200comprises a second embodiment display adapter 202, second embodimenthost software 224, and second embodiment client software 226. The hostsoftware 224 is configured to load into and run on a host computer 206that has a video port 238 (which may be HDMI, mini DisplayPort, or someother type of video port) and a host wireless adapter 230. The clientsoftware 226 is configured to load into and run on a client device 218with a client wireless adapter 232.

In the second embodiment accelerated secondary display system 200, datais communicated between host software 224 and client software 226 viathe host wireless adapter 230 and the client wireless adapter 232. Noextra hardware is needed in the second embodiment display adapter 202for the data channel between the host computer 206 and client device218. The second embodiment display adapter 202 has a display simulator222 connected to a video port 220 (HDMI). The adapter video port 220 isconfigured to connect via a cable to the HDMI video port 238 on of thehost computer 206.

Third Representative Embodiment

Another embodiment, shown in FIG. 3, is compatible with a host computerthat has a USB-A port and an HDMI port. The third embodiment acceleratedsecondary display system 300 comprises a third embodiment displayadapter 302, third embodiment host software 324, and third embodimentclient software 326. The host software 324 is configured to load intoand run on a host computer 306 that has a video port 338 that is HDMIcompliant and a data port 304 that is USB-A compliant. The clientsoftware 326 is configured to load into and run on a client device 318with a client data port 316.

In this embodiment, the display adapter 302 is connected to a video port320 (HDMI compliant) in the display adapter 302, which in turn isconnected to the video port 338 of the host computer 306. Thecommunication channel between the host software 324 and the clientsoftware 326 is a very simple wired connection—a cable connected to thehost computer's USB-A data port 304 passes through the display adapter302 into a USB-A data port 314 on the adapter, which in turn isconfigured to connect via a cable to a data port 316 on the clientdevice 318.

What is claimed is:
 1. An accelerated secondary display systemcomprising: a display adapter with a display simulator configured totransmit display characteristics; a host computer with a host computermemory storing host software, the host computer separate from thedisplay adapter and configured to connect with the display adapter via acable, the host computer configured to receive the displaycharacteristics, instantiate a frame buffer in the host computer memory,render an image with hardware acceleration into the frame buffer,maintain pixels of the image in the frame buffer, execute the hostsoftware, wherein the host software is configured to cause the hostcomputer to stream image data over a communication channel, the imagedata based on the pixels of the image in the frame buffer; a clientdevice with a screen and a client device memory storing client software,the client device separate from the display adapter and the hostcomputer, wherein the client software is configured to, when executed,receive the image data over the communication channel and present a copyof the image on the screen based on the image data; wherein the displaycharacteristics transmitted by the display simulator are generic displaycharacteristics; wherein the client software is configured to transmitdisplay characteristics that are client device display characteristics;wherein the host software is further configured to, when executed, causethe host computer to use the client device characteristics in renderingthe image and streaming image data; and wherein the host computer has anoperating system that is not specially modified to work with the displayadapter and host software.
 2. The accelerated secondary display systemof claim 1, wherein the display adapter further comprises a hub thatsplits an adapter data connection cable into an adapter data port and anadapter video port; wherein the display simulator is coupled to theadapter video port; wherein the host computer has a host data portcoupled to the adapter data connection cable; wherein the client devicehas a client data port coupled to the adapter data port; and wherein thecommunication channel is carried by the adapter data connection cable,the adapter data port and the client data port.
 3. The acceleratedsecondary display system of claim 2, wherein the adapter data port isUSB-A compliant; and wherein the video port is compliant with one ofHDMI (High-Definition Multimedia Interface) and mini DisplayPortcompliant.
 4. The accelerated secondary display system of claim 1,wherein the host computer has a host wireless adapter; wherein theclient device has a client wireless adapter; and wherein thecommunication channel is carried by the host wireless adapter and theclient wireless adapter.
 5. The accelerated secondary display system ofclaim 1, wherein the display adapter further comprises an adapter videoconnection cable coupled to the display simulator; wherein the hostcomputer has a host video port coupled to the adapter video connectioncable; wherein the host computer has a host data port; wherein theclient device has a client data port coupled to the host data port; andwherein the communication channel is carried by the host data port andthe client data port.
 6. The accelerated secondary display system ofclaim 1, wherein the display adapter further comprises an adapter videoport coupled to the display simulator, and an adapter video connectioncable coupled to the adapter video port; wherein the host computer has ahost video port coupled to the adapter video connection cable; whereinthe display adapter further comprises an adapter data port; wherein thehost computer has a host data port; wherein the client device has aclient data port coupled to the host data port through the adapter dataport; and wherein the communication channel is carried by the host dataport and the client data port.
 7. The accelerated secondary displaysystem of claim 1, wherein the host software is further configured tostream audio data to the client software.
 8. The accelerated secondarydisplay system of claim 1, wherein the client software is furtherconfigured to stream audio data to the host software.
 9. The acceleratedsecondary display system of claim 1, wherein the client software isfurther configured to stream client image data from a camera in theclient device to the host software.
 10. The accelerated secondarydisplay system of claim 1, wherein the client software is furtherconfigured to stream data to the host software that includes one or moreof: client device native screen resolution, current orientation, andsupported protocol versions.
 11. The accelerated secondary displaysystem of claim 1, wherein the host software is further configured tosend raw pixel data as the image data.
 12. The accelerated secondarydisplay system of claim 1, wherein the host software is furtherconfigured to compress the image data, and the client software isconfigured to decompress the image data.
 13. The accelerated secondarydisplay system of claim 12, wherein the host computer has a centralprocessing unit (CPU) and a graphics processing unit (GPU); and whereinthe host software is further configured use parallel processing,splitting processing between the CPU and GPU when pixel copying from theimage, compressing and streaming image data.
 14. The acceleratedsecondary display system of claim 13, wherein the host software isfurther configured use parallel processing by causing the host computerto divide the frame buffer pixels into tiles.
 15. The acceleratedsecondary display system of claim 1, wherein the communication channelis wireless.
 16. The accelerated secondary display system of claim 1,wherein the communication channel is wired.